I'm considering buying the base 13 inch MBA to replace my aging MBP but had a question regarding RAM. The base 13 comes with 2GB, which is the same as in my MBP. When my MBP runs out of RAM it accesses the disk, which cripples performance. Wouldn't the flash drive on the Air resolve this? In other words wouldn't it theoretically have 128GB of RAM? Is it worth the extra $100 to get the 4GB?